... , which is based on coal, heavy oil, light oil or flammable gas as fuel, steam boiler,hot water. Working principle: The boiler ... , which is based on coal, heavy oil, light oil or flammable gas as fuel, heat conducting oil as heat carrier. Using recycled ... 3-6 month.steam boiler,hot water boiler Coal, Oil( Gas ) Fired Heaterthermal Boiler,steam boiler,hot water boiler